1. Field of the Invention
This invention relates to a method for interconnecting and encapsulating individual opto-electronically active cells of organic opto-electronic devices such as organic photovoltaic (PV) or organic light emitting diode (OLED) devices, to form encapsulated modules. More particularly, the invention relates to a one-sheet lamination method that interconnects and encapsulates an array of opto-electronic devices formed on a substrate to form an encapsulated organic opto-electronic device module.
Organic opto-electronic devices such as organic PV devices and OLED devices generally comprise an opto-electronically active layer, formed of one or more layers of electroluminescent or light absorbing material, which active layer is sandwiched, usually with one or more layers of a hole transporting material, between a cathode layer and an anode layer. In the case of an organic PV device, the active layer is typically formed of one or more light absorbing layers of, for example, a blend of donor and acceptor polymers as disclosed in U.S. Pat. No. 5,670,791, a blend of a donor polymer with a small molecule acceptor such as [6,6]-phenyl C61-butyric acid methyl ester (PCBM) or a blend of small molecules. An optional hole collecting layer of a material such as polystyrene-sulphonate-doped polyethylene-dioxythiophene (PEDOT:PSS) may be provided between the anode layer and the active layer. For an OLED device, the active layer is typically formed of one or more electroluminescent layers comprising a light emitting material such as a light emitting polymer (LEP), for example poly(p-phenylenevinylene) (PPV), or a light emitting low molecular weight (small-molecule) material such as aluminum tris (8-hydroxyquinoline) (Alq3). An optional hole injecting layer of a material such as PEDOT:PSS or a polyaniline derivative may be provided between the anode layer and the active layer.
2. Related Technology
Organic opto-electronic devices such as organic PV devices and OLED devices can be fabricated by conventional techniques, generally by deposition of layers of the functional materials by spin-coating, spray coating, dip coating, doctor blade coating and the like. If a plurality of devices is formed on a single substrate, such deposition is followed by selective removal of the materials from areas between devices where they are not wanted, such as by plasma etching or laser ablation. For example, WO 01/39287 discloses selectively removing material from a PEDOT layer by plasma etching.
Alternatively, functional materials may be deposited selectively only in the areas where they are wanted. Suitable techniques for such selective deposition include inkjet printing as disclosed in EP 0880303, screen printing, and laser induced thermal imaging.
A cross-section through a basic structure 100 of a typical prior art organic opto-electronic device is shown in FIG. 7a. A glass or plastic substrate 102 supports a transparent anode layer 104 of a transparent conductive oxide (TCO), for example indium tin oxide (ITO), on which is deposited a hole transport layer 106, an active layer 108, and a cathode 110. The hole transporting layer 106 helps match the hole energy levels of the anode layer 104 and the light active layer 108. The cathode layer 110 typically is of a metal such as aluminum and may include an additional layer immediately adjacent the active layer 108, for example an alkali halide layer such as a layer of lithium fluoride, for improved electron energy level matching. Alternatively, the cathode layer 110 may be located in direct contact with the active layer 108 if it is of a metal such as calcium that has a lower work function than aluminum. Contact wires 114 and 116 to the anode and the cathode respectively provide a connection to a power source or storage cell 118.
Opto-electronic devices such as OLED devices may be deposited on a substrate in an array of opto-active cells. For example, in the case of an OLED device array, the cells are pixels to form a single or multi-color pixelated display. As is known, in such displays the individual elements are generally addressed and written to by activating row and/or column lines to select the pixels. Conversely, in the case of a PV device matrix, the cells are photo-active cells which are addressed and from which photo-generated current is collected by conductive lines associated with rows and/or columns of the photo-active cells.
FIG. 7b shows a cross-section through a prior art opto-electronic matrix 150, in which like elements to those of FIG. 7a are indicated by like reference numerals. In the matrix 150, the opto-active layer 108 comprises a plurality of opto-active portions 152 and the cathode layer 110 comprises a plurality of mutually electrically insulated conductive lines 154, running into the page in FIG. 7b, each with an associated contact 156. Likewise, the anode layer 104 also comprises a plurality of anode lines 158, of which only one is shown in FIG. 7b, running at right angles to the cathode lines. Contacts (not shown in FIG. 7b) are also provided for each anode line.
FIG. 7c shows a simplified cross-section through a prior art opto-electronic matrix. Again, like elements to those of FIGS. 7a and 7b are indicated by like reference numerals. Since the opto-electronically active materials are susceptible to oxidation and moisture, the device is encapsulated in a metal can 111 which is attached by glue 113 onto contact layer 105, small glass beads within the glue preventing the contacts being shorted out.
A plurality of such opto-electronic devices may be fabricated on a single substrate 160, for example as shown in FIG. 7d. This substrate is patterned using a photoresist and organic layers 106, 108 are then deposited by spin coating before the cathode layer 110 is applied. However, since the spin coating technique is non-selective, that is it deposits a thin film of organic material uniformly across the substrate, material must afterwards be removed from where it is not wanted. In particular, the spin coated organic material must be removed from areas where the encapsulating can 111 will be attached to the substrate, and also from areas where electrical connections will be made to the devices. In FIG. 7d, horizontal and vertical strips or scribe lines 162 indicate where material is to be removed for attaching the can 111. The organic material may be removed mechanically, by scraping, or by using a wet chemical photolithographic process (relatively long and expensive) but the preferred method for removing the organic material is by laser ablation.
WO 04/057674, the contents of which are incorporated herein by reference, discloses the formation of an array of interconnected devices by forming a plurality of devices on a substrate, depositing metal connectors through a shadow mask to electrically connect neighboring devices and encapsulating the array with a glass cover carrying an epoxy adhesive.